Magnet valve

ABSTRACT

A magnet valve, especially for tank venting in motor vehicles, having at least one valve opening and having a valve member, which for opening and closing cooperates with the at least one valve opening and which, forming a magnet armature of an electromagnet, is disposed opposite a magnet core of the electromagnet, an exciter coil being disposed on a coil carrier that is disposed in a magnet housing and surrounds the magnet core, and a thread being provided in the magnet housing, which thread is screwed to a first male-threaded portion of the magnet core, wherein a second male-threaded portion is disposed on the magnet core, which male-threaded portion, as the magnet core is screwed into the magnet housing, forms a thread course in the coil carrier.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a 35 USC 371 application of PCT/DE 00/01362 filed onApr. 29, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an improved magnet valve, and more particularlyto such valves especially for tank venting in motor vehicles.

2. Description of the Prior Art

Magnetic valves for venting vehicles tanks are known and disclosed forinstance by German Patent Disclosures DE 42 44 113 A1, DE 196 11 886 A1,and DE 198 52 980.5. In such valves, the magnet core is axiallydisplaced in the magnet housing for adjustment purposes by being screwedinto the thread. Such an adjustment is disclosed for instance by U.S.Pat. No. 5,424,704 as well, but in that case the magnet core is screwedinto the plastic coil carrier.

In order after the adjustment to provide an anti-rotation element, it isknown to apply plastic layers, such as Tuflok or an adhesive, to thethread. Furthermore, anti-rotation elements by later welding or bycalking of the two threads to one another are also known.

Such anti-rotation elements require additional method steps forproducing the magnet core and therefore entail additional cost.Furthermore, severely fluctuating loosening torques caused by tolerancefluctuations of the magnet core and of the cup-shaped magnet housing aswell as of the plastic, in particular Tuflok or adhesive, layer areproblematic.

Finally, an anti-rotation element of this kind is also vulnerable totemperature fluctuations and vibrational stresses.

SUMMARY OF THE INVENTION

An object the present invention is to provide a magnet valve of thisgeneric type which, in a simple way, enables adjustment with maximuminvulnerability to temperature fluctuations and vibrational stresses aswell as tolerance fluctuations between the magnet core and the magnethousing, and to prevent relative rotation of the magnet core.

The further male-threaded portion on the hollow-cylindrical magnet coreadvantageously forms its own thread course in the coil carrier withoutmetal-cutting machining and presses itself in, in a manner fixed againstrelative rotation, thus in a simple way attaining an optimalanti-rotation element, and because the adhesive or plastic layers knownfrom the prior art are dispensed with, the tolerances of only twocomponents now have to be taken into account for the anti-rotationelement, and these can be made more secure in process terms with a viewto production. Furthermore, an anti-rotation element of this kind hasloosening torques that can be readily adjusted. Furthermore, thisarrangement has substantially higher strength than a thin layer ofplastic or adhesive that is employed in anti-rotation elements knownfrom the prior art. The precision of adjustment is preserved because themagnet core is screwed into the metal magnet housing.

BRIEF DESCRIPTION OF THE DRAWING

Further advantages and characteristics of the invention will be apparentfrom the detailed description contained herein below taken with thesingle drawing for sure which is, a longitudinal section through a valveaccording to the invention, shown schematically.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One exemplary embodiment of a valve, shown in longitudinal section inthe drawing, is used for metered admixture of volatilized fuel from thefuel tank of a mixture-compressing internal combustion engine withexternally supplied ignition (not shown), into the engine, for instanceinto an intake tube, or in the case of direct gasoline injectiondirectly into an engine cylinder, and is part of a fuel vapor trappingsystem, not shown in further detail, of an internal combustion engine.The construction and function of such fuel vapor trapping systems can belearned for instance from Bosch Technische Unterrichtung MotormanagementMotronic [Bosch Technical Instruction, Motronic Motor Management], 2ndEdition, August 1993, pages 48 and 49. A tank venting valve and itsfunction can be learned for instance from the above mentioned Germanreferences, DE 42 44 113 A1 and DE 196 11 886 A1.

The tank venting valve has a two-part valve housing 10, with acup-shaped housing part 101 and a cap-like housing part 102 closing offthe housing part 101. The housing part 101 has an inflow stub 11 forconnection to a venting stub of the fuel tank, or to anactivated-charcoal-filled reservoir downstream of it for the volatilizedfuel. The housing part 102 has an outflow stub 12 for connection to theintake tube of the engine. The inflow stub 11 and the outflow stub 12are each disposed axially, for instance aligned with one another, in thehousing parts 101, 102. An electromagnet 13 is disposed in the interiorof the cup-shaped housing part 101.

The electromagnet 13 has a cup-shaped magnet housing 14, with a coaxialhollow-cylindrical magnet core 15 that penetrates the cup bottom andwith a cylindrical exciter coil 16, which is seated on a coil carrier 17of plastic that surrounds the magnet core 15 in the magnet housing 14.Embodied on the bottom of the metal magnet housing 14 is anoutward-protruding threaded stub 18 with a female thread 19, which isscrewed to a first male-threaded portion 21 of the hollow-cylindricalmagnet core 15. Thus by rotation in the magnet housing 14, the magnetcore 15 can be axially displaced highly exactly for adjustment purposes,because of the metal-to-metal screw fastening. The magnet core 15 isaligned with the inflow stub 11, so that volatilized fuel flowing inhere flows directly through the magnet core 15.

To achieve an anti-rotation function, a second male-threaded portion 35is disposed on the magnet core 15, in the region of the coil carrier 17;when the magnet core 15 is screwed into the female thread 19 disposed onthe threaded stub 18, this second male-threaded portion forms its ownthread course in the coil carrier 17 without metal-cutting machining.The coil carrier 17 here has a carrier sleeve 36, which has a throughopening 37, which for instance is graduated, and whose diameter is forinstance greater than the diameter of the first male-threaded portion 21of the magnet core 15, so that here the magnet core 15 is inserted fromabove, with the end that has the first male-threaded portion 21 leading,through the through opening 37 in order to come into contact with thefemale thread 19 of the threaded stub 18. As the first male-threadedportion 21 is screwed into the threaded stub 18, the secondmale-threaded portion 35 then cuts into the through opening 37 of thecarrier sleeve 36 and forms an anti-rotation element. An anti-rotationelement of this kind has high strength, is simple to produce, and makesreadily adjustable loosening torques possible. In particular, additionalmaterials for the anti-rotation element that are known from the priorart, such as adhesive or plastic layers, can be dispensed with.

The edge of the magnet housing 14 is angled to form an annular bearingflange 20. Received on the bearing flange 20 is a valve seat body, whichforms a short-circuit yoke 22 of the electromagnet 13 and which coversthe magnet housing 14 and rests peripherally on the bearing flange 20.In the short-circuit yoke 22 that forms the valve seat body, valveopenings are provided, which can be closed by means of a valve member 27that acts as a magnet armature and is disposed between the short-circuityoke 22 and the magnet core 15. Centrally in the valve member 27,coaxially with the hollow-cylindrical magnet core 15, an axial throughopening 28 is provided through which volatilized fuel arriving from theinflow stub 11 can reach the outflow stub 12 when the valve openings areopen. The valve member 27, made from magnetically conductive material,is disposed, spring-loaded in the valve closing direction, in thedirection of the outflow stub 12.

The stroke of the valve member 27 is adjusted by means of the axialdisplacement of the magnet core 15. Because of the metal-to-metal screwfastening of the magnet core 15 on the threaded stub 18, only negligiblyslight changes in the valve member stroke result even in the event oftemperature changes. By comparison, the plastic-to-metal screw fasteningbetween the magnet core 15 and the carrier sleeve 36 upon a temperaturechange brings about an increase in the relative rotation prevention,because of the different coefficients of thermal expansion.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

I claim:
 1. In a magnet valve, especially for tank venting in motorvehicles, having at least one valve opening and having a valve member(27), which for opening and closing cooperates with the at least onevalve opening and which, forming a magnet armature of an electromagnet(13), is disposed opposite a magnet core (15) of the electromagnet (13),an exciter coil (16) being disposed on a coil carrier (17) that isdisposed in a magnet housing (14) and surrounds the magnet core (15),and a thread (19) being provided in the magnet housing (14), whichthread is screwed to a first male-threaded portion (21) of the magnetcore (15), the improvement comprising a through opening (37) having nothreads disposed in the coil carrier (17), and a second male-threadedportion (35) disposed on the magnet core (15), which secondmale-threaded portion (35), as the magnet core (15) is screwed into themagnet housing (14), engages and forms a thread course in the coilcarrier (17) for rotation prevention.
 2. The valve of claim 1 whereinthat the second male-threaded portion (35) forms the thread course inthe coil carrier (17) without metal-cutting machining.